Boath was born in London. His father is a banker and his mother is a producer. He has an older brother, Jack and a younger sister, Millie. Boath attended the Catholicprep school St Phillip's. He has attended drama classes with his siblings for several years. His only acting experience prior to The Mummy Returns was lip-synching John Travolta's role in a class production of Grease.

Boath also starred in an ITV1 show called The Children. He played 14-year-old Jack, a troubled teenager, where he said he could relate to the character as his parents divorced when he was young too. In 2010 he played King Henry II as a teenager in The Pillars of the Earth.

Boath also had a small role in the third season of House of Anubis, playing Ben.